President Donald Trump defended his tough stance on immigrants crossing the U.S. border with Mexico on Saturday, praising his administration for a job well done and saying his approach will make the United States stronger.

Trump, who was in Las Vegas to lend support to U.S. Senator Dean Heller of Nevada, a Republican who is facing a stiff challenge to re-election, has been under fire for a policy that separates children from their parents when they illegally cross the U.S. border with Mexico.

Amid a fierce outcry, Trump reversed himself on Wednesday and signed an executive order to abandon the policy, but the fate of more than 2,300 children already separated from their parents before the order was enacted is unknown.